package org.frameworkset.soa;

import java.io.IOException;
import java.io.Reader;

public class BBossStringReader  extends Reader {

	private String str;
	private int length;
	private int next = 0;
	private int mark = 0;

	/**
	 * Creates a new string reader.
	 *
	 * @param s  String providing the character stream.
	 */
	public BBossStringReader(String s) {
		this.str = s;
		this.length = s.length();
	}

	/** Check to make sure that the stream has not been closed */
	private void ensureOpen() throws IOException {
		if (str == null)
			throw new IOException("Stream closed");
	}

	/**
	 * Reads a single character.
	 *
	 * @return     The character read, or -1 if the end of the stream has been
	 *             reached
	 *
	 * @exception  IOException  If an I/O error occurs
	 */
	public int read() throws IOException {

			ensureOpen();
			if (next >= length)
				return -1;
			return str.charAt(next++);

	}

	/**
	 * Reads characters into a portion of an array.
	 *
	 * @param      cbuf  Destination buffer
	 * @param      off   Offset at which to start writing characters
	 * @param      len   Maximum number of characters to read
	 *
	 * @return     The number of characters read, or -1 if the end of the
	 *             stream has been reached
	 *
	 * @exception  IOException  If an I/O error occurs
	 */
	public int read(char cbuf[], int off, int len) throws IOException {

			ensureOpen();
			if ((off < 0) || (off > cbuf.length) || (len < 0) ||
					((off + len) > cbuf.length) || ((off + len) < 0)) {
				throw new IndexOutOfBoundsException();
			} else if (len == 0) {
				return 0;
			}
			if (next >= length)
				return -1;
			int n = Math.min(length - next, len);
			str.getChars(next, next + n, cbuf, off);
			next += n;
			return n;

	}

	/**
	 * Skips the specified number of characters in the stream. Returns
	 * the number of characters that were skipped.
	 *
	 * <p>The <code>ns</code> parameter may be negative, even though the
	 * <code>skip</code> method of the {@link Reader} superclass throws
	 * an exception in this case. Negative values of <code>ns</code> cause the
	 * stream to skip backwards. Negative return values indicate a skip
	 * backwards. It is not possible to skip backwards past the beginning of
	 * the string.
	 *
	 * <p>If the entire string has been read or skipped, then this method has
	 * no effect and always returns 0.
	 *
	 * @exception  IOException  If an I/O error occurs
	 */
	public long skip(long ns) throws IOException {

			ensureOpen();
			if (next >= length)
				return 0;
			// Bound skip by beginning and end of the source
			long n = Math.min(length - next, ns);
			n = Math.max(-next, n);
			next += n;
			return n;

	}

	/**
	 * Tells whether this stream is ready to be read.
	 *
	 * @return True if the next read() is guaranteed not to block for input
	 *
	 * @exception  IOException  If the stream is closed
	 */
	public boolean ready() throws IOException {

			ensureOpen();
			return true;

	}

	/**
	 * Tells whether this stream supports the mark() operation, which it does.
	 */
	public boolean markSupported() {
		return true;
	}

	/**
	 * Marks the present position in the stream.  Subsequent calls to reset()
	 * will reposition the stream to this point.
	 *
	 * @param  readAheadLimit  Limit on the number of characters that may be
	 *                         read while still preserving the mark.  Because
	 *                         the stream's input comes from a string, there
	 *                         is no actual limit, so this argument must not
	 *                         be negative, but is otherwise ignored.
	 *
	 * @exception  IllegalArgumentException  If {@code readAheadLimit < 0}
	 * @exception  IOException  If an I/O error occurs
	 */
	public void mark(int readAheadLimit) throws IOException {
		if (readAheadLimit < 0){
			throw new IllegalArgumentException("Read-ahead limit < 0");
		}

			ensureOpen();
			mark = next;

	}

	/**
	 * Resets the stream to the most recent mark, or to the beginning of the
	 * string if it has never been marked.
	 *
	 * @exception  IOException  If an I/O error occurs
	 */
	public void reset() throws IOException {

			ensureOpen();
			next = mark;

	}

	/**
	 * Closes the stream and releases any system resources associated with
	 * it. Once the stream has been closed, further read(),
	 * ready(), mark(), or reset() invocations will throw an IOException.
	 * Closing a previously closed stream has no effect.
	 */
	public void close() {
		str = null;
	}
}
